1. Field of the Invention
This invention relates to a work conveying system for conveying works along a car body assembling line.
2. Description of the Related Art
In an automobile manufacturing factory, a conveying system including hanger units is used to convey works such as side body panels to be assembled into a car. Such conveying system carries the works by holding them by hanger units. FIG. 6 of the accompanying drawings shows an example of such conveying system. The conveying system comprises a support unit, a hanger unit, and an opening-and-closing mechanism.
The support unit supports the hanger units, and includes a pair of guide rails 2 installed on an immovable member 1 of factory building structures, drive members 4, and rollers housed in drive members 4.
Each hanger unit is suspended from the support unit, and includes a hanger frame 3, rotatable shafts 5, pieces (6) extending orthogonally of the moving direction of the frame 3, and hanger arms 7 extending downwardly from the frame 3 so as to sandwich a work therebetween.
The opening-and-closing mechanism, which is located at work loading areas so as to control the operation of the hanger units, includes supports 8, pressure cylinders 9, and movable arms 10. The opening-and-closing mechanism is secured to the immovable member 1 of the factory building structures. The pressure cylinders 9 are connected to the supports 8, to which movable arms 10 are coupled.
When the hanger unit reaches the work loading area, the opening-and-closing mechanism operates the pressure cylinders 9 so as to rock the movable arms 10, which then engage with the extending members 6 of the hanger unit, thereby moving the hanger arms 7 to their open positions.
With the foregoing opening-and-closing mechanism, the movable arms 10 control the rocking motion of the hanger arms. However, while the hanger arms are closed, i.e. while the hanger arms are sandwiching the work therebetween, they are not protected against their accidental rocking motion. Furthermore, the hanger arms might happen to be rocked by the weight of the work sandwiched therebetween.
Sometimes a distance between a pair of the guide rails for guiding the hanger units may be narrowed due to a limited available space for installing the work conveying system. In such a case, hanger units on adjacent conveying routes may interfere with one another, and the opening-and-closing mechanisms have to be installed substantially near the hanger units. Occasionally, the opening-and-closing mechanisms have to be located above the guide rails, which may prevent the movement of the hanger units on the guide rails. Furthermore, the foregoing opening-and-closing mechanisms are independently provided for the right and left hanger arms, respectively, which requires a lot of space in the factory.